U.S. patent application number 12/286846 was filed with the patent office on 2009-02-12 for earpiece with acoustic vent for driver response optimization.
This patent application is currently assigned to Ultimate Ears, LLC. Invention is credited to Jerry J. Harvey.
Application Number | 20090041262 12/286846 |
Document ID | / |
Family ID | 37830065 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090041262 |
Kind Code |
A1 |
Harvey; Jerry J. |
February 12, 2009 |
Earpiece with acoustic vent for driver response optimization
Abstract
An acoustically tuned earpiece is provided. Venting is performed
by boring a control port, separate from the output port, into the
driver. The diameter of the control port must be sufficiently small
to restrict the flow of air into and out of the driver, thus
isolating the acoustic performance of the driver from the volume
and/or the sealing capabilities of the earpiece enclosure. The
exact size of the venting port is selected to achieve the desired
acoustic performance. In all cases, the control port has a
cross-sectional area that is less than 25 percent of the
cross-sectional area of the driver's output port. In order to
optimize the size of the control port, an iterative process is
preferably used in which the cross-sectional area of the control
port is gradually increased while monitoring the performance of the
driver compared to a target response.
Inventors: |
Harvey; Jerry J.; (Lake
Ozark, MO) |
Correspondence
Address: |
PATENT LAW OFFICE OF DAVID G. BECK
P. O. BOX 1146
MILL VALLEY
CA
94942
US
|
Assignee: |
Ultimate Ears, LLC
Irvine
CA
|
Family ID: |
37830065 |
Appl. No.: |
12/286846 |
Filed: |
October 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11487856 |
Jul 17, 2006 |
|
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12286846 |
|
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60715001 |
Sep 7, 2005 |
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Current U.S.
Class: |
381/74 |
Current CPC
Class: |
H04R 1/1016 20130101;
H04R 1/26 20130101; H04R 1/22 20130101; H04R 1/1041 20130101 |
Class at
Publication: |
381/74 |
International
Class: |
H04R 1/10 20060101
H04R001/10 |
Claims
1. An earpiece comprising: an earpiece enclosure; at least one
driver disposed within said earpiece enclosure, said at least one
driver comprising: an output port; and a control port, wherein a
cross-sectional area of said control port is less than 25 percent
of a cross-sectional area of said output port, wherein said
cross-sectional area of said control port is sufficiently small to
restrict air flow into and out of said at least one driver during
operation and wherein said cross-sectional area of said control
port is sufficiently small to control an acoustic performance
corresponding to said at least one driver irrespective of a volume
corresponding to said earpiece enclosure; and an eartip
acoustically coupled to said output port of said at least one
driver.
2. The earpiece of claim 1, wherein said driver is an armature
driver.
3. An earpiece comprising: an earpiece enclosure; at least one
driver disposed within said earpiece enclosure, said at least one
driver comprising: an output port; and a control port with a
diameter of approximately 0.20 millimeters, wherein a
cross-sectional area of said control port is sufficiently small to
restrict air flow into and out of said at least one driver during
operation and wherein said cross-sectional area of said control
port is sufficiently small to control an acoustic performance
corresponding to said at least one driver irrespective of a volume
corresponding to said earpiece enclosure; and an eartip
acoustically coupled to said output port of said at least one
driver.
4. The earpiece of claim 3, wherein said driver is an armature
driver.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/487,856, filed Jul. 17, 2006, which claims
the benefit of U.S. Provisional Patent Application Ser. No.
60/715,001, filed Sep. 7, 2005, the disclosures of which are
incorporated herein by reference for any and all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates generally to audio monitors
and, more particularly, to in-ear monitors.
BACKGROUND OF THE INVENTION
[0003] Earpieces, also referred to as in-ear monitors and canal
phones, are commonly used to listen to both recorded and live
music. A typical recorded music application would involve plugging
the earpiece into a music player such as a CD player, flash or hard
drive based MP3 player, home stereo, or similar device using the
earpiece's headphone jack. Alternately, the earpiece can be
wirelessly coupled to the music player. In a typical live music
application, an on-stage musician wears the earpiece in order to
hear his or her own music during a performance. In this case, the
earpiece is either plugged into a wireless belt pack receiver or
directly connected to an audio distribution device such as a mixer
or a headphone amplifier. This type of monitor offers numerous
advantages over the use of stage loudspeakers, including improved
gain-before-feedback, minimization/elimination of room/stage
acoustic effects, cleaner mix through the minimization of stage
noise, increased mobility for the musician and the reduction of
ambient sounds.
[0004] Earpieces are quite small and are normally worn just outside
the ear canal. As a result, the acoustic design of the monitor must
lend itself to a very compact design utilizing small components.
Some monitors are custom fit (i.e., custom molded) while others use
a generic "one-size-fits-all" eartip.
[0005] Earpieces use either one or more diaphragm-based drivers,
one or more armature-based drivers, or a combination of both driver
types. Broadly characterized, a diaphragm is a moving-coil speaker
with a paper or Mylar diaphragm. Since the cost to manufacture
diaphragms is relatively low, they are widely used in many common
audio products (e.g., ear buds). In contrast to the diaphragm
approach, an armature receiver utilizes a piston design. Due to the
inherent cost of armature receivers they are typically only found
in hearing aids and high-end in-ear monitors.
[0006] Armature drivers, also referred to as balanced armatures,
were originally developed by the hearing aid industry. This type of
driver uses a magnetically balanced shaft or armature within a
small, typically rectangular, enclosure. A single armature is
capable of accurately reproducing low-frequency audio or
high-frequency audio, but incapable of providing high-fidelity
performance across all frequencies. To overcome this limitation,
armature-based earpieces often use two, or even three, armature
drivers. In such multiple armature arrangements, a crossover
network is used to divide the frequency spectrum into multiple
regions, i.e., low and high or low, medium, and high. Separate
armature drivers are then used for each region, individual armature
drivers being optimized for each region. In contrast to the
multiple driver approach often used with armature drivers,
earpieces utilizing diaphragm drivers are typically limited to a
single diaphragm due to the size of the diaphragm assembly.
Unfortunately, as diaphragm-based monitors have significant
frequency roll off above 4 kHz, an earpiece with a single diaphragm
cannot achieve the desired upper frequency response while still
providing an accurate low frequency response.
[0007] In order to obtain the best possible performance from an
earpiece, the driver or drivers within the earpiece are tuned.
Armature tuning is typically accomplished through the use of
acoustic filters (i.e., dampers). Further armature tuning can be
achieved by porting, or venting, the armature enclosure. Typically,
the driver is vented to a sealed, controlled volume. Diaphragm
drivers, due to the use of a moving-coil speaker, are generally
tuned by controlling the dimensions of the diaphragm housing.
Depending upon the desired frequency response, the diaphragm
housing may or may not be ported.
[0008] Although porting (i.e., venting) a driver to a controlled
volume allows the acoustic performance of an earpiece to be tuned,
it places relatively tight manufacturing tolerances on the
controlled volume of the earpiece, thus adding to the cost
associated with fabricating such high fidelity earpieces.
Accordingly, what is needed in the art is an earpiece that can
achieve the acoustic performance provided by porting to a
controlled volume without the added manufacturing complexity and
cost. The present invention provides such an earpiece.
SUMMARY OF THE INVENTION
[0009] The present invention provides an earpiece that is
acoustically tuned using at least one vented driver. Venting is
performed by boring a control port, separate from the output port,
into the driver. The diameter of the control port must be
sufficiently small to restrict the flow of air into and out of the
driver, thus isolating the acoustic performance of the driver from
the volume and/or the sealing capabilities of the earpiece
enclosure. The exact size of the control port is selected to
achieve the desired acoustic performance. In all cases, the control
port has a cross-sectional area that is less than 25 percent of the
cross-sectional area of the driver's output port. In at least one
preferred embodiment, the control port has a diameter of
approximately 0.20 millimeters, preferably with a tolerance of
.+-.0.03 millimeters.
[0010] In order to optimize the size of the control port, for
example during the design of a new earpiece, an iterative process
is preferably used. During this process the driver is
characterized, enlarged, and then re-characterized. The driver
characterizations before and after control port enlargement are
compared to a target driver response. If the pre-enlargement
control port provides better performance, relative to the target
response, then the pre-enlargement control port diameter is
selected as the optimized control port size. If the
post-enlargement control port provides better performance, relative
to the target response, then the iterative process continues.
[0011] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 illustrates an earpiece with a ported driver
fabricated in accordance with the prior art;
[0013] FIG. 2 illustrates a prior art earpiece similar to that
shown in FIG. 1, except for the use of a sealed enclosure coupled
to the ported driver;
[0014] FIG. 3 illustrates an earpiece in which the driver includes
a control port in accordance with the invention;
[0015] FIG. 4 illustrates an earpiece utilizing a pair of armature
drivers, each of which includes a control port;
[0016] FIG. 5 illustrates an earpiece similar to that shown in FIG.
4, except that only one of the drivers includes a control port;
and
[0017] FIG. 6 illustrates an optimization process used to determine
the optimal control port diameter for a particular driver
configuration and desired driver response.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0018] FIG. 1 is an illustration of a ported earpiece in accordance
with the prior art. In this particular configuration earpiece 100,
also referred to herein as an in-ear monitor and a canalphone,
includes a single armature driver 101. Driver 101 is coupled to a
source, not shown, via cable 103. Only a portion of cable 103 is
visible in FIG. 1. The sound that is produced by armature driver
101 exits an output port 105 and passes through a sound delivery
tube 107. Although not required by the prior art or the current
invention, in some configurations and as shown in the illustrated
configuration, the output end of sound tube 107 is coupled to a
damper 109, also commonly referred to as an acoustic filter. In
addition to providing a means of tuning the frequency response of
the earpiece, for example by reducing the output level for a
particular frequency range, damper 109 can also be used to reduce
the overall sound pressure level. The sound passing through damper
109, or directly from sound tube 107, enters sound delivery tube
111 of sound delivery member 113. At least a portion of sound
delivery member 113 is designed to fit within the outer ear canal
of the user and as such, is generally cylindrical in shape.
[0019] Attached to the end portion of sound delivery member 113 is
an eartip 115, also referred to as an eartip sleeve or simply a
sleeve. Additionally, and as known by those of skill in the arts,
eartip 115 or the combination of sound delivery member 113 and
eartip 115 can be replaced with a custom fit eartip (not shown). A
custom fit eartip is one that is designed to fit into a particular
user's ear. Custom fit eartips, which are left ear and right ear
specific, are made by first making a casting of the user's ear
canal and concha, and then molding the earpiece from the
casting.
[0020] Custom fit earpieces typically provide better performance,
both in terms of delivered sound fidelity and user comfort, than
generic earpieces. Generic earpieces, however, are generally much
less expensive as custom molds are not required and the earpieces
can be manufactured in volume. In addition to the cost factor,
generic earpieces are typically more readily accepted by the
general population since many people find it both too time
consuming and somewhat unnerving to have to go to a specialist,
such as an audiologist, to be fitted for a custom earpiece.
[0021] In the illustrated configuration, a generic eartip 115 is
shown. Eartip 115 can be fabricated from any of a variety of
materials including foam, plastic and silicon based material.
Eartip 115 can have the generally cylindrical and smooth shape
shown in FIG. 1, or can include one or more flanges. To hold eartip
115 onto member 113 during normal use but still allow the eartip to
be replaced when desired, typically the eartip includes a lip
portion 117 which is fit into a corresponding channel or groove 119
in sound delivery member 113. The combination of an interlocking
groove 119 with a lip 117 provides a convenient means of replacing
eartip 115, allowing sleeves of various sizes, colors, materials,
material characteristics (density, compressibility), or shape to be
easily attached to in-ear monitor 100. As a result, it is easy to
provide the end user with a comfortable fit at a fraction of the
cost of a custom fit eartip. Additionally, the use of interlocking
members 117 and 119 allow worn out eartips to be quickly and easily
replaced. It will be appreciated that other eartip mounting methods
can be used with earpiece 100. For example, eartip 115 can be
attached to sound delivery member 113 using pressure fittings,
bonding, etc.
[0022] An outer earpiece enclosure 121 attaches to sound delivery
member 113. Earpiece enclosure 121 protects driver 101 (or multiple
drivers) and any required earpiece circuitry (e.g., cross-over
circuit for multiple driver implementation) from damage while
providing a convenient means of securing cable 103, or alternately
a cable socket (not shown), to the in-ear monitor. Enclosure 121
can be attached to member 113 using interlocking members (e.g.,
groove 123, lip 125). Alternately, an adhesive or other means can
be used to attach enclosure 121 to member 113. Enclosure 121 can be
fabricated from any of a variety of materials, thus allowing the
designer and/or user to select the material's firmness (i.e., hard
to soft), texture, color, etc. Enclosure 121 can either be custom
molded or designed with a generic shape.
[0023] There are a variety of techniques that can be used to hold,
or mount, the components of the earpiece within earpiece enclosure
121. In the illustrated configuration, a boot member 127 is used to
hold damper 109, sound tube 107 and a portion of driver 101 in
place.
[0024] In addition to output port 105, driver 101 includes a
secondary port, or vent, 129. Port 129 opens up to sealed region
131, this region defined by the combination of housing 121 and
those earpiece components residing within, or coupled to, housing
121 (e.g., driver 101, cable 103, boot member 127 and the end
portion of sound delivery member 113). The volume of region 131
defines the acoustic impedance that port 129 is subject to and,
consequently, the frequency response of driver 101/earpiece 100. As
known by those of skill in the art, since region 131 is used to
control the back pressure that the driver is subjected to, the
diameter of port 129 must be large relative to output port 105, on
the order of at least 25 percent of the cross-sectional area of
output port 105 and more typically on the order of at least 100
percent of the cross-sectional area of output port 105.
Additionally it is known that the volume of region 131 must be
carefully controlled in order to allow the resonant peaks of an
earpiece to be controlled. Such control may be used, for example,
to improve the low frequency response of the earpiece.
[0025] Although sealed region 131 can be used to control the
acoustic performance of the earpiece, it will be appreciated that
maintaining a specific volume for region 131, especially for a mass
produced earpiece, is difficult. During manufacturing, a variety of
factors can alter the volume of region 131, thus altering the
acoustic performance of the earpiece. For example, if the sealant
and/or adhesive used to couple housing 121 to sound delivery member
113 extends into region 131 the volume of the region will be
impacted. Similarly, the length of cable 103 that extends into
region 131 and the fit of driver 101 within boot member 127 will
both affect the volume of the enclosed region. Additionally, tight
control of the manufacturing tolerances of the individual
components associated with region 131 must be maintained in order
to achieve a specific volume and thus the desired acoustic
performance.
[0026] In order to overcome the manufacturing variances that can
alter the volume of the region to which port 129 is coupled to and
thus better control the acoustic performance of a mass produced
earpiece, port 129 can be coupled to a controlled volume chamber
201 within housing 121 as shown in FIG. 2. Controlled volume
chamber 201 can be of any of a variety of shapes. Although the use
of chamber 201 makes it easier to vent the driver to a controlled
volume that is reproducible in a mass produced earpiece, it will be
appreciated that there is little room within an in-ear monitor for
inclusion of such a chamber. This is especially true if the
earpiece includes multiple drivers. In yet another alternate
configuration, port 129 can be coupled to free space, thereby
providing an infinite controlled volume. Note that the location of
port 129 in FIGS. 1 and 2 has been altered to clarify the figures
and is otherwise insignificant.
[0027] The inventor of the present invention has found that by
sufficiently decreasing the diameter of the venting port (e.g.,
control port 301 shown in FIG. 3), the port itself controls the
acoustic performance of the driver and thus the earpiece. It will
be appreciated that control port 301 must be sufficiently small to
restrict the flow of air into and out of driver 101, otherwise the
volume of the region within the enclosure will continue to affect
the acoustic performance of the earpiece. The exact size of the
control port is selected to achieve the desired acoustic
performance, typically optimizing low frequency sound by
controlling driver resonant peaks. In all cases, control port 301
is less than 25 percent of the cross-sectional area of output port
105. In at least one preferred embodiment of the invention, control
port 301 has a diameter of approximately 0.20 millimeters,
preferably with a tolerance of .+-.0.03 millimeters.
[0028] It will be appreciated by those of skill in the art that the
use of a control venting port (e.g., port 301) dramatically eases
the manufacturing tolerances placed on the earpiece as the volume
within enclosure 121 need no longer be carefully controlled from
earpiece to earpiece in order to achieve the desired acoustic
performance. Additionally, if the enclosure is leaky, i.e., not
completely sealed, the acoustic performance will not be affected,
as the volume within the region is not being used to control the
driver resonant peaks.
[0029] In addition to easing the manufacturing process, the use of
a control port as disclosed by this invention also simplifies
venting the individual drivers of a multi-driver earpiece.
Utilizing the invention, some or all of the drivers in the
multi-driver earpiece may be vented. For example, FIG. 4
illustrates an earpiece 400 that includes a pair of drivers
401/403. Drivers 401/403 include control ports 405/407,
respectively. Although not part of the invention, FIG. 4 also shows
a circuit 409, preferably comprised of a passive crossover circuit.
The passive crossover circuit divides the incoming audio signal
into a low-frequency portion electrically routed to driver 401 and
a high-frequency portion electrically routed to driver 403. Each
driver may or may not include an acoustic filter (i.e., a damper).
In the illustrated embodiment a first damper 411 is acoustically
coupled to driver 401 and a second damper 413 is acoustically
coupled to driver 403. For the sake of clarity, FIG. 5 illustrates
an earpiece identical to that shown in FIG. 4 except that only one
of the drivers, i.e., driver 401, includes a control port. This
approach can be used, for example, to alter only the frequency
response of the driver being used to drive the lower frequencies,
thus providing an effective means of further increasing the base
response of the earpiece.
[0030] Although the inventor has found that in a variety of
earpiece configurations a control port with a diameter of
approximately 0.20 millimeters is appropriate, when control port
size optimization is required, for example during the design of a
new earpiece configuration, the optimization process described
below and illustrated in FIG. 6 is preferred. The illustrated
process can be performed to a driver that is either separate from,
or integrated within, an earpiece. The first step (step 601) is to
characterize the driver (or drivers) frequency response for the new
earpiece. Once characterized, a small control port is bored (e.g.,
drilled) into the driver (step 603). Typically, the diameter of
this port should be as small as possible utilizing conventional
fabrication techniques. Preferably the initial port diameter is
less than 0.10 millimeters, more preferably less than 0.05
millimeters, and even more preferably approximately 0.01
millimeters. After the initial control port has been drilled into
the driver, the driver and/or earpiece assembly is re-characterized
(step 605). The response of the driver as well as the previously
characterized driver response are then compared to a target
response (step 607). The target response is the desired response
for the particular driver configuration, for example, one in which
the low frequency response is extended, a resonant peak is
controlled, etc. If the response is improved (step 609), the
diameter of the control port is increased by a pre-selected, and
relatively small, amount (step 611). Preferably the diameter of the
control port is increased by at least 0.02 millimeters, and more
preferably by approximately 0.01 millimeters. The driver is then
re-characterized (step 605) and the new response as well as the
previous response are then compared to the target response (step
607). This iterative process continues until a new response is
worse than the previous response (step 613). At this point the
previous control port diameter is selected as the optimal diameter
for this particular configuration and the desired target response
(step 615).
[0031] As will be understood by those familiar with the art, the
present invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof.
Accordingly, the disclosures and descriptions herein are intended
to be illustrative, but not limiting, of the scope of the invention
which is set forth in the following claims.
* * * * *